Make sure you are familiar with units for
Mass: kilogram (kg)
Distance: metre (m)
Speed: metre per second (m/s)
Acceleration: metre per second squared (m/s^2)
Force: newton (N)
Time: second (s)
Gravity: newton/kilogram (N/kg)
A distance time graph has distance on the y axis (usually in metres) and time on the x axis (usually in seconds). The gradient of the line (change in y/ change in x) is the speed. If the line is flat then the object is stationary.
To calculate average speed use
speed (m/s) = distance travelled (m)/ time taken (s)
Apparatus: stop watch and metre rule
mark the start and end positions for the know distance
use a metre rule to measure the distance
line up front of car with start point, release and start timer
move eyes to end point
stop timer when front of car passes end point
improve by repeating and averaging
make sure car starts from stationary
calculate average speed using : average speed = distance travelled/ time taken
on a velocity time graph the velocity-time graph the velocity is on the y axis (usually in m/s) and time is on the x axis (usually in s). If the line is flat then the object is moving at a constant velocity. the gradient of the line is the acceleration. The area under the line is the distance travelled.
Gradient = acceleration= change in y/ change in x = change in velocity/time
The area under the graph can be calculated as rectangles and triangles, or by counting boxes, is equal to the distance travelled.
Forces can act on a body to change the velocity, so the speed, direction or both.
Or forces can change the shape of a body, stretching it squishing it or twisting it.
different types of forces include:
Gravitational, weight, friction, electrostatic, air resistance (drag), tension (force in a spring), up thrust, lift, thrust
Friction is caused by surfaces rubbing. The force always acts in the opposite direction to motion.
Force = Mass x Acceleration.
the force refers to the resultant force or the combined forces as seen in 1.15
Weight (N)= Mass (kg) x gravitational field strength (N/kg)
gravitational field strength on earth is approx. 10 N/kg and in GCSEs is taken to be 10 N/kg.
Stopping distance = Thinking distance + Breaking distance
Thinking distance Affected by:
Tiredness
Alcohol
speed of the car
Drugs (avoid as drugs can increase or decrease thinking distance)
Braking distance affected by:
Road conditions
Tyre conditions
Brake conditions
speed of the car
mass of the car
unit for:
current : Ampere (A)
charge : coulomb (C)
resistance : ohm (Ω)
time : second (s)
potential difference : volt (V)
power : watt (W)
power (w) = current (A) x voltage (V)
when looking at a circuit a component will be given a power and a voltage appropriate to run at then the current can be calculated so the rating of the fuse can be selected for slightly higher than that.
AC is constantly changing magnitude and direction. AC is how mains electricity is produced from turbines.
DC is constant. And is produced from a battery and used in some sensitive components like in computing.
Notes on current:
in the bellow diagram the red box could represent a wire, a bulb, a resistor or a diode.
By changing the resistance of the variable resistor the graphs are reproduced.
Since V = IR, as you increase the resistance in a circuit, the current will decrease.
A lamp can be added to a circuit to check for a current. If current is flowing, the lamp will light up.
Potential difference (V) = Current (A) x Resistance (Ω)
current is rate of flow of charge so I=Q/t
Electrons are negatively charged and free to flow in a metal so carry charge
VT = V1 + V2
IT = I1 = I2
RT = R1 + R2
the units for:
angle = degree (°)
frequency = hertz (Hz)
wavelength = metre (m)
velocity = metre/second (m/s)
time = second (s)
Key Definitions:
Waves can transfer energy and information with out transferring matter, for example sun light, it transfers energy as it makes the earth warm without bringing any matter.
wave speed (m/s) = frequency (Hz) x Wavelength (m)
You will need to use any of the in 3.05 and 3.06 to solve problems to do with sound waves and electromagnetic (light) waves
Electromagnetic Spectrum:
Radio Waves
Microwaves
Infrared (IR)
Visible Light
Ultraviolet (UV)
X – Rays
Gamma Rays
these are written in order of increasing frequency, lowest at the top
and decreasing wavelength, lowest at the bottom.
the colours displayed are in order of lowest frequency to the left highest frequency to the right.
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uses of electromagnetic radiations, including: |
the detrimental effects of excessive exposure of the human body to electromagnetic waves:
• microwaves: internal heating of body tissue
• infrared: skin burns
• ultraviolet: damage to surface cells and blindness
• gamma rays: cancer, mutation
to reduce the risks:
light is a transverse wave that can be reflected and refracted
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1. Set up your apparatus as shown in the diagram using a rectangular block. 2. Shine the light ray through the glass block 3. Use crosses to mark the path of the ray. 4. Join up crosses with a ruler 5. Draw on a normal where the ray enters the glass block 6. Measure the angle of incidence and the angle of refraction and add these to your results table 7. Comment on how the speed of the light has changed as the light moves between the mediums. 8. Repeat this for different angles of incidence and different glass prisms. |
Total Internal Reflection:
Critical Angle:
sound waves are longitudinal waves which can be reflected and refracted.
know the units for
Mass = kilogram (kg)
energy = joule (J)
velocity = metre/second (m/s)
acelleration = metre/ second 2 (m/s2)
force = newton (N)
time = second (s)
power = watt (W)
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Energy Stores: Chemical – e.g. the food we eat Kinetic – movement energy Gravitational – objects that are lifted up Elastic – e.g. from springs Thermal – from hot objects Magnetic – objects in magnetic fields Electrostatic – charged objects Nuclear – stored within a nucleus
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In any process energy is never created or destroyed. (It is just transferred from one store to another.)
The energy flow is shown by arrows whose width is proportional to the amount of energy involved. The wasted and useful energy outputs are shown by different arrows.
Work Done (J) = Force (N) x distance moved (m)
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Work done = energy transferred |
Gravitational potential energy (J) = Mass (kg) x gravitational field strength (N/kg) x height (m)
